Topographic plans show the physical properties of a site. They assist architects, engineers, and planners at the design stage of land development process. Some of the features shown on plans of topography are ground elevations, walkways, ditches, swales, catch basins, manholes, retaining walls, curbs, trees, and any others that are of significance to the project. On larger sites contour lines may also be generated to better illustrate the profile of the ground surface.